Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method for access control in a wireless communication system and apparatus for supporting the same.
Related Art
3GPP (3rd generation partnership project) LTE (long term evolution), which is an improved version of UMTS (universal mobile telecommunications system), is introduced as 3GPP release 8. The 3GPP LTE uses OFDMA (orthogonal frequency division multiple access) in the downlink (DL) and uses SC-FDMA (single carrier-frequency division multiple access) in the uplink (UL). MIMO (multiple input multiple output) having the maximum 4 antennas is employed. Recently, 3GPP LTE-A (LTE-advanced), which is an improved version of 3GPP LTE, is under discussion.
The quality of the service, which is currently provided to a user equipment (UE), may be deteriorated due to the mobility of the UE as a mobile device, or a cell capable of providing a better service may be sensed. Hence, the UE may be moved to a new cell, and such an operation is called the movement of the UE. The UE may select a cell on the same frequency, a cell on a different frequency, or a different RAT (radio access technology) cell and move to the corresponding cell.
When an UE attempts connection establishment in order to have an access to a network, whether to allow the access may be controlled, which is called an access control. The access may be controlled according to the service related to the access to the network.
If the situation reaches confusion state due to the increase of the random access load, an access class barring (ACB) may be used. The ACB is a method capable of controlling a random approach of the UE depending on the access class (AC) to which the UE belongs. A base station may broadcast an ACB-related parameter as a part of system information at regular intervals. This parameter includes a barring factor and barring time. The barring factor is a probability value between 0 and 1, which determines whether to block a random access when the network is overloaded. A UE desiring an approach to the network generates a random number between 0 and 1, and when this random number is smaller than the barring factor, the access is attempted, and otherwise the access is blocked. The blocking time is the average time for which the UE stands by until a random approach blocked by the ABC is attempted again.
Meanwhile, the applications used by the UE are associated with an appropriate service class by the criteria such as required quality of service (QoS) and a traffic distinction rule. And, information for access control and parameters are provided depending on the service class.
However, even though applications for public safety or new applications may be associated with the same service class according to the criteria such as required QoS, traffic distinction rule and the like, it may be necessary for the access probability to be differently applied depending on the importance or urgency.